Carrier telegraph system



Dec. l, 1942. w, A; PHELPS 2,304,017

CARRIER TELEGRAPH SYSTEM Filed July 29, 1941v sheets-.sheet 1 M F/G. 3 FnfouE/vcr f uw UN /2 .sf/va ,we 9 F/rfn T0 y 29 L THE@ END REL ra orf/fn :22 I SEND AMM' SENID CCTS. H om' `2a 20 ha l0 f' DE n 2 i I M I \PoL4R/zfo 4.5 4ad y E Recs/vf RELAY 3325 32] POLAR/ZEP N oec. nec. H

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CARRIER TELEGRAPH SYSTEM I Filed July 29, 1941 2 Sheets-Sheet .2

BAND 65' zig F/G. 2 l y G vy' 'l ro OTHER GEA/59470195 /M/E/VTOR TWO PHASE, souecf aF BASE Ffuwcf Patented Dec. 1, 1942 CARRIER TELEGRAPH SYSTEM Walter A. Phelps, Madison, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 29, 1941, Serial No. 404,479

6 Claims.

This invention relates to a carrier current telegraph system, and more particularly to an arrangement for controlling the phase relationbetween the carrier current waves utilized in a multiplex carrier wave system.

In multiplex carrier Wave telegraph system involving the transmission of a relatively large number` of individual carrier current Waves, which may be harmonics of a wave of a base frequency, on a single transmission line embodying repeaters in order to provide a number of carrier channels corresponding to the number of carrier current Waves, it has been found that the peaks of such waves tend to add up periodically to produce relatively high amplitudes that overload the repeaters. This is due to the gradual change in the relative phases of the carrier Waves of the several channels. Such peaking of the carrier waves causes the production of undesirable modulation and intermodulation components extending over the frequency range of the signaling Waves thereby causing a low signalto-interference ratio in all signaling channels. Heretofore, such overloading has been partially overcome by the general scheme of synchronizing the generators of the several carrier current Waves with the Wave of base frequency in order to x the phase relation between the former Waves, and then reversing the leads of certain generators to produce a reversal of phase ofthe individual waves supplied thereby. A diiculty with such phase adjustment is that the phase change is limited to 180 degrees. In the development of new multichannel carrier current systems, such phase adjustment may be inadequate unless the repeaters are designed at further expense to embody a certain amount of extra loadcarrying capacity to compensate for the inadequacy of the phase adjustment effected by lead reversals alone.

Specically, one arrangement to prevent repeater overloading consists in the yuse of a harmonic generator energized by a wave of base frequency and arranged to apply its output to the control grids of a number of vacuum tube oscillators to control the latter such that the waves of individual frequency supplied thereby are synchronized with the desired harmonics of the base frequency. A phase shifter in the output of each oscillator then permits the adjustment of the phase of the Wave supplied thereby. This controls the hereinbefore-described addition of the peaks of the individual Waves so as to prevent overloading of the line repeaters. Another arrangement to prevent repeater overloading involves the provision of a carrier current source comprising a motor-driven inductor alternator in Which each individual rotor produces a wave of different frequency, the rotors having numbers of teeth bearing a harmonic relation strip to each other. As all rotors are rigidly attached to the same shaft, the several Waves of diierent frequencies generated thereby Will be in synchronism with the wave of base frequency. However, it is not practical with such an arrangement to make an exact adjustment of the relative phases of' the several waves generated, and it has, therefore, been necessary to depend upon a random phasing of the several Waves to prevent the occasional production of excessive current peaks in the repeaters. l

The present invention contemplates an arrangement for controlling the phase angles of individual carrier current waves in multiplex signaling systems.

The main object of the invention is to control the phase relation between a plurality of carrier current Waves being transmitted on the same line.

Another object is to prevent overloading oi line amplifiers embodied in multiplex carrier current systems.

A further object is to supply a plurality of carrier current waves to a transmission linesuch that the phase angles of individual Waves may be varied in an expeditious manner.

Still another object is to simplify the design of multiplex carrier current signaling systems.

A still further object is to minimize undesirable modulation effects in a carrier current signaling system utilizing a large number of carrier kcurrent Waves.

Another object is to maintain the signal-tointerference ratio in all channels of a multiplex carrier current signaling system at tolerable minimum levels.

In a specific embodiment of the present invention, each carrier Wave Agenerator comprises an electron device including a predetermined rnumber of anodes and an electron beam to move thereover, and a multipole stator disposed` externally of the device to actuate the electron beam. The individual stators are energized from a common source of electrical energy of certain frequency so that all electron beams are actuated in synchronism with the frequency thereof. The output frequency of each electron beam generator is equal to n times the frequency of the common source, where n is the number of anodes.

L: The individual electron devices are `positioned in a preassigned manner with respect to each other in their associated stators such that corresponding anodes of each of the electron devices are presented to the synchronized electron beams with a certain time interval therebetween to control the phase relation between the carrier current Waves being transmitted on the line.

The invention will be readily understood from the following description taken together with the accompanying drawings, in which:

Fig. 1 is a schematic circuit showing one terminal of a duplex carrier current telegraph system to which the invention is expeditiously applicable;

Fig. 2 is a schematic circuit illustrating an electron beam carrier current generator which may be employed in practicing the invention in connection with Fig. 1;

Fig. 3 embodies curves representing action obtainable in Figs. 1 and 2 both with and without practicing the invention; and

Fig. 4 is a schematic representation of the invention embodied in Fig. 2. Referring to Fig. 1, a generator 8 of alternating current sine waves of frequency fs, which is the third odd multiple of a base frequency f supplied by a source 1 and which will be hereinafter explained, is applied through `a' sending circuit I2, channel filter I8'and line transformer I4 to an outgoing transmission line I5-embodying one or more thermionic amplifiers 26 of suitable type. A subscribers sending and receiving loop 20 includes source 2| of direct current potential whose negative terminal is grounded, sending and receiving apparatus 22, winding ofv sending relay 23, winding of break relay-24 and ground 25. The sending relay 23 embodies armature 29, marking contact 21 and spacing contact 28.

The wave generator 8 illustra-ted in Fig. 2 is an electron beam tube 55 of a type disclosed in the patent of A. M. Skellett, No. 2,217,774, granted October 15, y1940, and comprising a cathode 55, cathode heater 51, control grid 58, a plurality of screen electrodes 59, a plurality of suppressor grids 68, and a plurality of anodes 8|. The respective screen and suppressor electrodes 59 and 65, control grid 58 and anodes 6i are disposed about the cathode 56 in a curvilinear path. v The screen electrodes 59 are connected to the positive terminal of a source 52-of direct current potential whose negative terminal is grounded. The suppressor electrodes 68 are connected to ground 63. Adjacent anodes'il joined by individual links 64 are applied over lead 65 and primary winding 65 of an output transformer 61 to the positive terminal of a source 59 of direct current potential whose negative terminal is grounded. The secondary winding 58 of the transformer 51is impressed across the input of a filter 13.

Positioned externally of but concentrically with the tube 55 is a magnetic stator 18 formed of iron and having four equally spaced poles 1I each of which has applied thereon a coil 12. The stator 18 may be of a depth equal substantially to the lengthvof the above-mentioned electrode assembly. DiametricallyV opposite coils 12 are connected and poled so as to produce magnetic poles of opposite polarity. As shown in Fig. 2, diametrically opposite pairs of coils 12, 12 are connected to individual phases of a two-phase source 1 of'alternating current voltage having the two phases adjusted to be 90 degrees apart and having-a certain frequency. These two phasesmay be derived from a two-phase generator wound for the purpose or they may be derived from a single phase using a capacitor individual to each pair of coils 12, 12, both of which methods are disclosed in the Skellett patent, supra. This produces within the space defined by the stator poles a magnetic field which rotates in synchronism with the frequency of the two-phase source 1.

In this magnetic eld is disposed the radial electron beam tube 55 in which electrons from the cathode 56 are focussed on the individual anodes 6I, successively, as the radial beam 14 rotates in synchronism with the rotating magnetic field as explained in the Skellett patent, supra. As the electric field drawing the electron beams from the cathode 56 to the anodes 6l is produced by a direct potential applied to all anodes 6I, the rotating electron beam consists of tWo oppositely directed beams which will have the effect merely ofy providing two parallel paths for space current. The rotating beam 14 produces a pulsating current idealized in Fig. 3A, in the primary winding 68 of the transformer B1, Fig. 2. In this connection a certain amount of separation is provided between the individual anodes 6I, depending on the amount of overlap of the electron beam 14 between adjacent anodes BI.

In general, this ovelap prevents the pulsating current from dropping to zero between successive pulses as illustrated in Fig. 3E but, however, such direct current component is removed by the effect of the transformer 61. It is tobe understood that the respective screen and suppressor electrodes 59 and 60 perform the same function as corresponding electrodes in thewell-known pentode tube. The pulsating current applied to the primary winding 68 of the transformer 51 induces in the secondary winding 68 thereof a current whose frequency is n times the frequency of the two-phase source 1, where n is the number of individualanodes 6| in the electron tube 55. Band filter 13, Fig. 2, connected to the secondary winding 68 serves to remove the direct current component and harmonics of the `base frequency and so to smooth out the wave of the current therein so that such wave has a substantially sine form as illustrated in Fig. 3B.

In Fig. 2, the electron beam tube 55 and associated stator 18, transformer 61, and filter 13 are assumed to constitute the wave generator 8 of Fig. 1. As the wave generators Q-I, Fig. 1, are assumed to be duplicates of the wave generator 8, the former are therefore assumed to comprise individually the elements identified above as constituting the Wavegenerator 8. The generators 8, 9-10 are caused to produce alter nating current waves having different frequencies by varying the number of individual anodes Gi, as pointed out above. Thus, the frequency change effected by each wave generator 8, @-35 is equal to the frequency of the two-phase source 1 multiplied by the number of individual anodes 6l. Assuming the two-phase power source 1 to -have a frequency of cycles per second, then the successive frequencies of the Wave generators 8, S-IU could comprise odd multiples of 85 beginning with the third and ending with the nth, that is, frequencies f3, fs-fn, by appropriately Varying the number of individual anodes 5i in each of the electron beam tubes 55, Fig. 2, constituting therespective wave generators 8, 9'l(i. As the Wave generators 8, 9--I are synchronized with the two-phase sourceA 1, the individual electron beams are therefore driven in synchronism with the respective. harmonics. of the irequencyi the two-phase source i. 'l

Reierrine again to Fig. 1., incoming. transmis..-

Sion line. 3i! embodying one. or more. thermionic` amplifiers 'itY of suitable type is connected through line transformer 3i, channel iilter 3.2, amplier-detector 3.3 and. winding of Yreceiving relay 34 Whose armature 3,5 has one terminal connected over lead 3i to the balanced loop cir- Cuit 20 Marking contact 3,1 of the receiving relay 34 is connected over lead 38. to a common point, 39, thence over lead il tothe negative terminal of; source 4l of direct, currentvoltage Whose positive terminal is. grounded, and over lead 421 to Spacing contactV fi- 3; of the break relay 2:4. Marking contact 44 of thelatter relay is connected bylead d5; to the positive terminal of source 4.6 of direct current voltage whose negative terminal is, grounded. Spacing contact 41; of the receiving relay 34 is extended by. a lead d8 tothe armature 49. of the break relay 2d. It is understood that the subscribers apparatuspointed out abover in connection. with the, Wave. generator 8` is also duplicated in the same. manner for the individualv Wave generators. S-HL In the operation of Fig, 1, a subscriber transmits individual signaling. elements by actuating hissending. apparatus 22tto operate the armature 29v associated with the respective sending relay toits marking and spacingV contacts. The a1'- mature. 29 when. closed on. the markingA contact 21, short-circuits resistanceon onel side of the sending. circuit i2'l to apply eiectively Waves f3 from the Wave source 8 tothe outgoing line l5; and thearmature. 29, when closed` on theV spacing contact 28, is connected in shunt of the sending circuit l2 thereby` effectively disconnecting the wave source 8 from theoutgoing line-|5130 prevent theapplication ofthe waves fs thereto. v

Waves fsV` fromY a. remote subscriber-s station, not shown, incoming on the-line3 are selected by the filter 32, amplied and rectied in the usual manner in the amplier-rectier- 33, and thereafter-*utilized toactuate the armature 35- of the receiving relay 34 to-its. respectivemarking andspacing contacts 31 and iii. eiect corresponding actuations oi the subscribers sending anclreceiving apparatus 22. This operation is Well-understood in-the art. AtA the same time a` distant subscriber` may send a break signalto the subscriber, thensending, to interrupt such operation in` order to-gain-control ofsig-nal transmission. Such break signal serves to operate the armature 35 ofy the receiving relay 34 to itsspacing contact lil, thus applying a positive battery to theapex :til-ofl the balanced loop circuitl. Actuation--ovthe-key of sending and receiving apparatus 22, then no longer causes operation of the sending relay 23 which remains on its marking contact- 2i. This operation is disclosed inv the patent of A. Weaver, No. 1,569,055, granted January 12, 1926.

In the above operation of Fig. 1, the wave generators- 8, 9-l provide Waves f3, fs-,fn which.65

This serves to that overload momentarily the line ampliers 28 in the manner explained in my copending application, Serial No. 356,123 filed September i0, 1940,

In accordance with the present invention, the Wave generators 8, 9-10 are mutually arranged such that a certain phase relation is provided between the Waves f3, fs-fn being transmitted on the outgoing line I5. To accomplish this, the several tubes 55 constituting Wave generators 8, S-ID are positioned in their associated stators 'i8 in a preassigned manner to vary the phase angles of the individual Waves f3, .f5-fn in a manner that Will be presently described.

In this connection, Fig. 3A shows the successive undirectional pulses a, b, c impressed on the primary Winding 66 of the transformer 81 as the electron beam M moves over the successive anodes 6| in Fig. 2; and the curve 3B shows the correspondingly successive alternations d, e, g in the output of filter 13, Fig. 2. For the curves of both Figs. 3A and 3B the tube 55 is assumed to be so positioned in its associated stator T that the location of the anodes 6| may be represented by the solid line segments of Fig. ll.

Next, the tube 55 is rotated in itsassociated stator 'iii in a clockwise direction by an amount such that the anodesiiil are caused to assume the positions shown by the broken line segments in Fig. 4. Now the electron beam 'ifi passes over substantially the mid-point of the middle anode 6l, as illustrated in the broken lines in Fig. 4, at a later time than over the mid-point, of this segment when in its initial position. For the. purpose of this description, it is assumed that the previously mentioned rotation of the tube 55 in` its stator l' as represented in Fig. 4 causes a SiO-degree shift of the corresponding anodes 5i. Referring to Fig. 3C, it is seen that the successive unidirectional pulses a, b', c corresponding to the successive pulses a, b, C of Fig. 3A are irnpressed degrees later on the primary winding,

66 of the transformer 5i. Consequently; the successive alternations d', e', g," of 3D occasionedby the pulses af, b', c of Fig. 3C, arealso effective 90. degrees later at the output of' the filter 13, Fig. 2. l In other Words, the respectivel unidirectional pulses of.SCgandalternations of 3D are eiective at the output `of thelter, i3, Fig. 2, substantially 90 degrees later than the correspondingly respective unidirectional pulses cab, c of Fig. 3A and alternations d, e, gof Fig. 3B.

It is apparent that the tube55 may be shifted.

in its associateds'tator. in clockwiseV or counterclockwise directions to provide echange in the phase angle -of'the Wave .f3 in the output ci theA lter 13 `extendingl somewhere between 0 and 360 degrees.

Wave generators..ieand` lil-.as previously pointed out may be individually.t rotatedin their associated stators 'lain preassignedzarnounts toprovide the Waves fs-fn With dierent phase angles.

As lthe electron beams or the individual .tubes are synchronized `with the. frequency ofgthebase.-

Wavesource the adjustments .ofthe individual. electron beam tubes .55 in a preassigned: manner.

in the associated .stators Titi;- constituting the respective Wave generators. 3,. 9`;i!) serve to present corresponding:individualanodes.. 5l of: the several electron devices 55; to the synchronized electron beamsfidtwith a certa.in.time. intervalv between each correspondinganodedi .to provide.-

eachA Wavefa, fe'fefn .with a. certain ..phase angl-e. Accordingly, a certain phase relation may be Accordingly, the electrozrbeam tubey and associated elementsin Fig. constituting the.

provided between the waves fz, fs-fn on the outgoing line l5. Thus, controlling the time difference between corresponding unidirectional pulses of the wave generators '8, S-IU in the manner explained above in connection with Figs. 3 and 4, enables control of the phase relation between the waves fa, .f5-.fn on the line l5.

A suitable cathode ray oscillograph applied to the line l5 may be utilized to observe such phase relation sol as to determine which of the waves, if any, requires further phase adjustment and the amount thereof. As the wave generators 8, 9-I ll are synchronized with the frequency of `the base-wave source 1, the waves fa, fs-fn will tend to maintain the preassigned phase relation on the line i5 thereby to minimize deleterious effects on transmission in the entire system in the manner discussed in my copending application, supra.

It is understood that the individual electron beam tubes shown in Fig. 2 may be so mounted mechanically with a suitable scale that they can be readily rotated through relatively small angles until the optimum relative angular positions are found. Then, the individual electron beam tubes may be locked in their respective positions. Such optimum relative angular positions may be realized when the lowest possible peaks are attained as all carrier current Waves are simultaneously applied to the sending line l5.

It is further understood that while the invention is disclosed with individual electron beamV tubes, it is not necessarily limited thereto, and would operate equally satisfactorily with the several individual pluralities of anodes and associated electron beamv combined in a singie envelope; and in addition that individual stators may be calibrated such that a preassigned time difference between individual waves may be initially provided. In the latter connection, such time difference is understood to mean a preassigned time difference between corresponding anodes of individual electron devices.

What is claimed is:

1. In combination, a utilization circuit, means to apply a plurality of discrete alternating current waves of diierent frequencies to said circuit, said wave means comprising a plurality of individual electron devices, each embodying a predetermined number of targets and an electron beam to move thereover, and means of certain frequency to actuate said electron beams in synchronism therewith, corresponding targets of individual electron devices being oriented with respect to time so as to be presented to associated electron beams at different time intervals to control the phase relation between said Waves in said circuit. 2. In combination, a transmission line, means to generate a plurality of discrete alternating current waves of different frequencies, and signaling means to control the effective application of said waves to said line, said wave generating means comprising a plurality of individual electron devices each embodying a certain number of anodes, and an electron beam, and electrical means of specific frequency to actuate said electron beams in synchronism therewith over said anodes, including a stator disposed externally of each of said devices such that therein said devices occupy a preassigned relation with respect to each other to present corresponding anodes of each of said devices to said electron beams in a certain time relation to control the phase relation between said waves on said line.

. 3. vIn combination, atransmission line, vmeans Source.

to generate a plurality of discrete alternating' current waves of different frequencies, and signaling means for controlling the effective application of said discrete wave generating means to said line, said wave generating means comprising a plurality of electron devices, each embodying a certain number of anodes disposed in a curvilinear path, an electron beam to move thereover, and a multipole stator concentrically positioned externally of said electron device to move said electron beam over said anodes, and a common source of alternating current voltage of certain frequency to energize simultaneously said stators to synchronize said movement of said electron beams with said certain frequency of said common source, said devices being individually positioned in a preassigned manner with respect to each other in said stators to present corresponding anodes of each said devices to said synchronized electron beams at different timey intervals to control the phase angles of individual waves of said plurality of Waves on said line.

4. An alternating current telegraph system comprising a line, means to generate a plurality of discrete alternating current Waves of different frequencies for transmission on said line, and means to control effectively the application of said waves to said line to represent individual signaling elements, said wave generating means comprising a plurality of individual electron tubes each embodying a predetermined number of targets, an electron beam to move thereover, and a stator concentrically disposed externally thereof, and a `common source of alternating cur- :rent voltage of .certain frequency to energize said stators of said plurality of tubes toV cause said electron beams to move in synchronism with the frequency of said source so that each of said tubes produces an alternating current wave whose frequency is equal to the product of the number of said anodes and said certain frequency, said tubes being individually positioned in said stators in a preassigned manner with respect to each other to present corresponding anodes of each of said tubes to said synchronized electron beams with a preassigned time difference between each of said corresponding anodes to control the phase relation between said waves on said line.

5. In combination in a circuit to produce a group of alternating current waves having a predetermined phase relation therebetween, a'plurality of groups of targets arranged such that corresponding targets of individual groups have a preselected electrical time relation, an electron beam individual to each group of targets-and movable thereover, and meansA comprising an alternating voltage of certain frequency to move said electron beams in synchronism over said targets.

6. In combination, in a circuit to supply alternating current waves having a predetermined phase relation therebetween, means to produce a plurality of alternating current waves, comprising a plurality of electron devices each embodying a plurality of targets and an electron beam movable thereover, said devices occupying such relative positions that corresponding targets of individual devices possess preselected relative electrical time, and a source of alternating voltage of certain frequency to move said electron beams in synchronism at the certain frequency of said WALTER A. PHELPs. 

